Well many of those in work will agree with them then. IME, in all sorts of jobs at all levels, working for someone else is very likely to be sh*te.
My last job was a very very flexible part-time one, doing stuff I loved, though overstretched as I was doing my co-worker's work - she was on LT sick. I have mh issues, and have always found f/t employment led to clinincal depression. Iin spite of the extreme stress of that job I managed to do my job well, and earn the equiv of ~£25K pro rata ie about 12K. It helped that I was employed by a well-known mh charity, who of course really did understand.
So working was shite, because of the stress of the circumstances, but not because of the people I worked with. When I was TUPEed, same job different employer, my working conditions were unsuitable (confidential work in an office shared with another group), and most managers had little understanding of the difficulties I was facing. I too went LT sick, and then onto ESA (CB). From my job being bearably shite but kind of enjoyable, it turned into my job being unendurable.
I realise my mh must make a difference here - but when I was young I looked forward to being able to work, I thought it would clear my depression, which I had since childhood, not make it ten times worse. I made it into my ideal job, university lecturer, but am glad now depression stopped my progression. Working in a uni has now become another shite job, either not paid to research, or having to churn out publications for the sake of it, teaching mixed ability students...